A. Field of the Invention
The present invention relates to machines and apparatus for forming ultrasonic wire bonds on miniature workpieces such as microcircuits and read/write heads of the type used to read and write data from and to disk memories. More particularly, the invention relates to an automatic ultrasonic bonding machine having an ultrasonic bonding tool which protrudes downwardly from a vertically tiered stack of orthogonally translatable tool support platforms, each having a separate motor drive, which when driven by computer generated command signals, automatically translates the tool in three dimensional space to thus position a wire end protruding from the tool tip at precisely pre-determined locations on a workpiece and form ultrasonic bonds at those locations by energizing an ultrasonic transducer rigidly coupled to the upper end of the tool.
B. Description of Background Art
A large variety of scientific procedures, medical procedures and industrial processes require the use of a type of apparatus referred to generally as a micro-manipulator for the precise positioning of a tip of a tool or instrument relative to a small workpiece or other such object. For example, the manufacture of electronic components such as integrated or hybrid microcircuits requires the use of a micro-manipulator-type apparatus, for the following reasons.
Integrated circuits are fabricated from thin slices of a semi-conducting material such as silicon, germanion, or from gallium arsenide or other III-V compounds, i.e., compounds of elements from columns three and five of the periodic table. The slices are cut into small squares or rectangles referred to as chips or dice, ranging in size from squares about 100 mil (0.100 inch) on a side to several hundred mils. Transistors, diodes, resistors and interconnecting circuit paths are formed on each chip or die by diffusing impurities into selected regions of the die to produce a desired electrical conductivity. Various conducting paths and insulated layers are then deposited on the chip.
After a semi-conductor chip or die has been fabricated as described above, it must be attached to a base or carrier. A lid is then sealed to the base to form a package or container which protects the delicate die from damage. Prior to attaching the lid to the carrier which supports the die, conductive pads which provide input and output conductive paths to the die must be electrically interconnected to more robust leads or terminals which extend outward from the carrier. These interconnections are customarily made using fine aluminum or gold wires. The wires are ultrasonically or thermo-sonically welded to the pads and external leads by a bonding tool that applies ultrasonic energy, or a combination of heat and ultrasonic energy, to a bonding site. Since the connection pads of a microcircuit are extremely tiny and closely spaced, great precision is required in positioning the tip of a bonding tool relative to the microcircuit.
Responsive to the need for an apparatus capable of precisely positioning the tip of an ultrasonic transducer to form wire bonds on microcircuit chips, the present inventor invented a micro-positioner apparatus which employs a novel pantograph-type manipulator input mechanism. That apparatus, which was disclosed in the present inventor""s U.S. Pat. No. 3,474,685 and issued on Oct. 28, 1969, has proven to be highly effective in performing its intended functions, and wire bonding machines employing the novel design concepts including the pantograph mechanism disclosed in that patent are widely used throughout the electronics industry. However, the present inventor found that certain aspects of the micro-positioner disclosed in the 3,474,685 patent might be improved upon. For example, the allowable working or throat depth of the ultrasonic tool tip would preferably be larger for certain bonding applications. Also, the use of offset pivotable mountings for the transducer tool support plate would desirably be minimized, thereby minimizing the requirement for springs to counter balance unbalanced forces exerted in supporting the tool support plate by offset mountings. Moreover, it would be desirable to have a micro-positioner apparatus in which various ultrasonic transducers and other bonding tool accessories such as wire spooling mechanisms, some of which might be substantially heavier than conveniently supportable by prior art micro-positioners, could be used. Such a need arises, for example, in bonding tie heavier wires required for connection to certain electronic components such as wound coils and disk drive components. In response to those considerations, the present inventor disclosed a Micro-positioner For Ultrasonic Bonding, U.S. patent application Ser. No. 08/773,637 filed Dec. 24, 1996, now U.S. Pat. No. 5,871,136. In that patent the present inventor disclosed a micro-positioner apparatus having a pantograph-like input manipulator mechanism, and a follower mechanism coupled to the input manipulator mechanism by a ball joint and supporting an ultrasonic transducer housing and bonding tool on a tool support plate. The tool support plate is longitudinally slidably mounted on a tool support guide plate, allowing fore and aft motion of the tool tip. The tool support guide plate is in turn pivotably supported by a yoke having a yaw pivot bearing which allows lateral motion of the tool tip. The yoke is in turn supported by a pitch pivot bearing having a horizontally disposed pivot axis, thereby permitting pivotal motion in a vertical plane of the yoke, tool support plate, and tool tip. By a suitable choice of spacings between the pivot axes of the pantograph input manipulator mechanism, support bearings and ball joint, the tip of the bonding tool is caused to move in coordinate directions of a second coordinate system containing the tool tip in precisely scaled ratios of corresponding motions in a first coordinate system of an input control knob on the input manipulator mechanism. The combination of a longitudinally slidable tool support plate with two pivot bearings orthogonal to each other and to the platform axis, provides a micropositioner apparatus which has both a rugged construction capable of supporting heavy loads on the tool support plate, and a substantial throat depth. In a preferred embodiment of the disclosed apparatus, the longitudinal platform axis of the tool tip, and the pivot axes of the pitch and yaw pivot bearings all intersect at a common point, thereby assuring completely orthogonal motions of the tool tip in three orthogonal coordinate directions that are precisely scaled fractions of corresponding input control knob motions.
In U.S. patent application Ser. No. 09/153,206, filed Sep. 15, 1998, now U.S. Pat. No. 6,164,514, the present inventor disclosed a micro-manipulator for ultrasonic bonding applications having a manipulator input mechanism and tool holder follower mechanism which are both pendent from an overlying support structure, thereby affording a work space of potentially unlimited lateral extent below the apparatus. Among other advantages, the large work space can accommodate workpieces located on a conveyor belt disposed below the apparatus.
The micro-manipulator apparatus disclosed in the pending application identified above provides means for dynamically positioning an implement relative to a workpiece, particularly an ultrasonic bonding tool tip relative to a miniature electronic component, moving the tool tip into contact with a selected bonding site to permit formation of a bond by application of ultrasonic energy to the bonding site, and withdrawing the tip upon completion of the bond. A preferred embodiment of a micro-manipulator apparatus according to the prior invention disclosed in the pending application includes a manually operable manipulator input mechanism coupled by means of a ball joint to a follower mechanism which includes a tool support structure for holding an ultrasonic bonding tool or similar implement. Position commands input to the manipulator input mechanism, as for example, by human manipulation of a control knob comprising an input element of the mechanism, are coupled to the follower mechanism, resulting in motions of the tool tip that are precisely scaled fractions of the input position commands. According to the prior invention, motions of an input member of the manipulator mechanism in an input coordinate system effect precisely ratioed motions of a tool tip in an output follower coordinate system. The apparatus according to the prior invention could have as few as one degree of freedom for both the input and output follower coordinate systems. Preferably, however, the input manipulator had three degrees of translational freedom along three orthogonal coordinate axes of an input coordinate system, resulting in translational motions of a tool tip along three orthogonal axes of the output follower coordinate system.
According to one aspect of the prior invention, the follower mechanism is mounted to a support structure by means of at least two mutually orthogonally disposed linear bearing sets, one set for each degree of tool-tip freedom. In a preferred embodiment of the prior invention, a primary bearing platform structure is linearly movably fastened to a vertical support structure by means of first linear bearing means, a secondary or intermediate bearing platform structure is linearly movably fastened to the primary bearing platform structure by second linear bearing means having a line of action orthogonal to that of the first linear bearing means, and a tertiary bearing platform structure is linearly movably fastened to the secondary platform support structure by third linear bearing means having a line of action orthogonal to those of both the first and second bearing means. A tool such as an ultrasonic bonding tool is fastened to the third bearing platform structure, which thus comprises a tool support member.
In a preferred embodiment of the prior invention, three bearing support platform structures forming a cascaded series are used, with the primary bearing platform structure being vertically movably fastened to a vertical support structure wall by a pair of parallel, longitudinally opposed, vertically disposed linear roller bearings. The secondary or intermediate bearing support platform structure is laterally movably fastened to the underside of a laterally outwardly protruding, horizontally disposed leg of the primary bearing platform structure by a pair of parallel, longitudinally opposed, laterally disposed roller bearings. The tertiary, tool-support bearing support platform structure is longitudinally slidably fastened to the underside of the intermediate platform support by a pair of parallel, laterally opposed, longitudinally disposed linear roller bearings.
Also in the preferred embodiment of the prior invention, the tool support platform is horizontally disposed, movable in a fore and aft, longitudinal direction and supports near the front longitudinal end thereof an ultrasonic force transducer having a downwardly depending tool tip for contacting a workpiece such as an electronic microcircuit.
According to the prior invention, the manipulator input mechanism is located to the rear of and at a higher elevation than the follower mechanism, and is coupled to the follower mechanism by a ball joint. The ball joint includes a ball which protrudes upwardly from the rear longitudinal end of the tool support platform and a socket which protrudes downwardly from a manipulator input mechanism cross member. With this construction, the lowest component surface of the apparatus may be the bottom surface of the tool support platform. Since the tool support platform is coupled through overlying cascaded bearing support platform structures to a support structure at a location at a higher elevation than the tool support platform, a work space of potentially unlimited lateral extent is provided beneath the apparatus.
Preferably, an ultrasonic transducer of the prior invention is resiliently fastened to the tool support platform, allowing the transducer and tool tip to move upwards when the tip is moved downwards into contact with a bonding site, thereby limiting the downward force exerted by the tip on the bonding site. As disclosed in the prior application, resilient upward displacement of the transducer may also be used to activate a switch connected to control circuitry which inputs a pulse of current of pre-determined duration to the transducer. By including a four-bar linkage between the tool support plate and resilient transducer mounting resilient displacements of the tool tip are constrained to occur only in a vertical direction.
The micro manipulator disclosed in the present inventor""s pending application No. ""206 provides a highly satisfactory solution to the problem of efficiently forming ultrasonic bonds on workpieces requiring a large clearance space below the line of action of a manually controlled ultrasonic bonding tool, such as workpieces located on a conveyor belt. However, the problem of making a sequence of ultrasonic bonds at precisely pre-determined locations on tiny workpieces located on moving conveyor belts still remained. For example, the manufacture of read/write heads used in magnetic disk memories requires the formation of permanent electrical connections between conductive pads on a surface of a tiny magnetic field sensing chip located at the outer end of support member referred to as a slider, and conductors in the form of conductive strips disposed inwardly along the surface of the slider to electrical terminals which are used to connect the head to read//write circuitry of disk drive electronics.
The conductive pads on the magnetic field sensor chip are typically located on a side of the chip disposed perpendicularly outwardly from the conductive strips on the surface of the platforms. Thus, bonds between each slider conductor and an adjacent sensor chip pad are, according to one technique, made by first applying a flame or an electrical arc discharge to the end of a fine wire protruding from the bore of an ultrasonic ball-bonding tool to melt the wire, which upon cooling resolidifies into a fusion ball. The tool and ball are then moved along a line action directed diagonally into a corner formed between the surface of the sensor chip and the slider until the ball contacts both the chip pad and adjacent slider conductor. Ultrasonic energy is then applied through the tip of the tool to the ball, welding the ball to both the chip pad and slider conductor. The bonding tool is then retracted from the bond site, and the wire grasped by mechanical jaws and pulled to break the wire at the bond site. Another fusion ball is then formed at the broken end of the wire protruding from the tool, and the tool tip and wire again moved diagonally into the corner defined between the upper surface of the slider and the adjacent transverse surface of the sensor chip to form the second and any other subsequent bonds required for the read/write head. This method of ultrasonically bonding conductive elements of read/write heads for magnetic memories is understandably referred to as xe2x80x9cball-in-the-cornerxe2x80x9d bonding.
Because of the extremely small size and perpendicular orientation of the surfaces of conductive pads to be bonded, ball-in-the-corner bonding requires a bonding tool to be positioned with extreme accuracy relative to the workpiece. Moreover, the prodigious volumes of read/write heads required by the computer industry virtually dictates that such bonds be made at high production rates, e.g., on an assembly line in which the heads are transported via a conveyor belt to and from an ultrasonic bonding machine. Since the design of presently used ultrasonic bonding machines results in a relative limited work space being available beneath the bonding tool tip, read/write heads on which ball-in-the-corner bonds are to be made must be individually removed from a conveyor belt and transported to a bonding machine for bonding. Thus, a problem with bonding methods using currently available bonding machines is the interruption of assembly line work flow, specifically the interruption of transport of parts by conveyor through assembly line work stations. This interruption is caused by the requirement for removing workpieces from the conveyor belt for bonding, and returning them to the conveyor belt after completion of the bonding process. Accordingly, it would be desirable to provide a bonding machine which could make ultrasonic bonds on workpieces while they remain on a conveyor belt, without having to remove the workpieces from the conveyor belt. In particular, to maximize the throughput rate of ultrasonic bonding on large quantities of small workpieces, it would be desirable to provide an ultrasonic bonding machine which could make bonds on individual workpieces located in longitudinally spaced apart rows of workpieces arranged transversely across the surface of a conveyor belt, motion of the belt being halted during formation of bonds on the row of workpieces. Accordingly, the present invention was conceived of to provide an ultrasonic bonding machine for automatically moving the tip of an ultrasonic wire bonding tool into contact with a sequence of precisely pre-determinable locations of a workpiece, and forming a sequence of ultrasonic bonds at those locations at high rates.
An object of the present invention is to provide a machine for automatically positioning an ultrasonic bonding tool at precisely pre-determined locations relative to a workpiece, and forming ultrasonic bonds at those locations.
Another object of the invention is to provide an automatic ultrasonic bonding machine for automatically moving the tip of an ultrasonic bonding tool to contact pre-determined locations of a workpiece and forming ultrasonic bonds thereat.
Another object of the invention is to provide an automatic ultrasonic bonding machine which employs a cascaded stack of orthogonally translatable support platforms to translate a tip of an ultrasonic bonding tool protruding downwardly from the stack relative to a workpiece located below the tool tip.
Another object of the invention is to provide an ultrasonic bonding machine including an upper support member, and a stack of orthogonally translatable support platforms which depend downwardly from the upper support member, each of the support platforms being drivable by a separate actuator motor under automatic control to a precisely pre-determined location relative to a workpiece located below an ultrasonic bonding tool which protrudes downwardly from the end tool support platform of the stack.
Another object of the invention is to provide an automatic ultrasonic bonding machine which includes an ultrasonic tool having a central longitudinally disposed bore for receiving a length of bonding wire, a pair of opposed clamp jaws above the bonding tool for grasping the bonding wire and pulling the wire to break it off at a bond site, a drag tube including a radiused capillary bore for frictionally resisting motion of a bonding wire supplied from a spool through the tube, pivot actuator means for pivoting the clamp jaws and drag tube to thereby extend the broken end of the wire a precisely pre-determined distance below the lower end of the bonding tool tip, and an electric flame-off torch pivotable to a position below the broken end of the bonding wire to form thereat a fusion ball of pre-determined characteristics.
Another object of the invention is to provide an automatic ultrasonic bonding machine including a first, upper Y-axis tool support platform rollably supported underneath a fixed support structure, a second, X-axis tool support platform rollably supported underneath the Y-axis tool support platform, a third, Z-axis tool support platform rollably supported at the front of the Y-axis tool support platform, a rear transducer mount support plate pivotably mounted to the front of the Z-axis tool support platform, a transducer mount assembly pivotably mounted to the front of the rear transducer mount support assembly, and a clamp/feed tube/drag tube assembly pivotably mounted to the upper surface of the transducer mount assembly.
Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims.
It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims.
Briefly stated, the present invention comprehends an automatic ultrasonic bonding machine for automatically forming ultrasonic wire bonds at a sequence of pre-determined locations of a workpiece at high throughput rates.
An automatic ultrasonic bonding machine according to the present invention includes an upper support plate fastenable to an overlying support structure which may be located above a conveyor belt, for example. The automatic ultrasonic bonding machine according to the present invention includes a positioning mechanism for moving the tip of an ultrasonic bonding tool by drive motors to precisely pre-determinable positions within a three-dimensional coordinate space containing a workpiece, e.g., in X-Y directions parallel to the workpiece, and in a third coordinate direction, e.g., the Z-direction downwardly to contact a bond site on a workpiece with the tool tip and form thereat an ultrasonic bond, and upwardly to withdraw the tip from the bond site. The positioning mechanism includes a generally downwardly tiered stack of tool support platforms comprising a first, upper, Y-axis tool support platform translatable horizontally in a first, Y-direction with respect to an overlying support plate, a second, X-axis tool support platform located below the Y-axis tool support platform and translatable horizontally in a second, X-direction relative to the Y platform, and a third, Z-axis tool support platform located in front of the X-axis tool support platform and translatable in a Z-direction relative to the X-axis platform.
The first, upper translatable tool support platform of the positioning mechanism is rollably attached to the lower surface of the upper support plate by a first pair of laterally opposed, parallel linear roller bearings which enable linear motion of the upper tool support platform in a first direction parallel to a work surface, e.g., in a xe2x80x9cYxe2x80x9d direction parallel to the surface of a conveyor belt located below the machine, and longitudinally or perpendicularly disposed to the conveyor belt travel direction. The positioning mechanism also preferably includes a second, intermediate translatable tool support platform linearly rollably attached to the lower surface of the upper translatable tool support platform by a second pair of longitudinally opposed, i.e., front and rear, parallel linear roller bearings. The latter bearing pair enables linear motion of the intermediate tool support platform in a second direction, perpendicular to the first translatable direction, e.g., in an xe2x80x9cXxe2x80x9d direction parallel to a conveyor belt travel direction.
The positioning mechanism of the automatic ultrasonic bonding machine according to the present invention also includes a third, front translatable tool support platform linearly rollably attached to the front surface of the intermediate translatable tool support platform by a third pair of laterally opposed, vertically disposed parallel linear roller bearings. The latter bearing set enables linear motion of the front tool support platform in a third coordinate direction perpendicular to the first and second translating directions of the first and second tool support platforms, i.e., in a xe2x80x9cZxe2x80x9d direction perpendicular to a workpiece support surface such as a conveyor belt.
A preferred embodiment of an automatic wire bonding machine according to the present invention includes a rear generally horizontally disposed transducer mount support plate which protrudes forward from the front, Z-axis translatable tool support platform. The rear transducer mount support plate has a generally rectangular shape, and is pivotably mounted near the rear or inner transverse edge wall thereof, by a pair or first, upper rear pivot joints, between a pair of laterally opposed, vertically elongated rectangular buttress walls which protrude forwardly from the Z-axis translatable tool support platform.
The rear transducer mount support plate is provided with a shallow rectangularly-shaped notch which protrudes rearwardly from the front edge wall of the plate and forms at laterally opposed edges thereof a pair of short laterally opposed, parallel rectangular bar-shaped arms which protrude forward from the rear transverse edge wall of the notch. A front transducer mount assembly is pivotably mounted in the notch between the arms, by a pair of second, upper front pivot joints. The latter include a pair of laterally opposed conical bearing pins which protrude laterally inwardly from the end of each of the two arms, the inner ends of the bearing pins being received by a pair of opposed roller bearings fixed in the upper ends of a pair of vertically disposed rear webs of the transducer mount assembly. One of the webs is pivotably coupled near the lower end thereof by a third, front lower pivot joint to the front end of a horizontally disposed lower linkage bar. The rear end of the lower horizontal linkage bar is pivotably coupled to the inner side of a longitudinally aligned one of the two buttress walls which protrude forward from the Z-axis tool support platform and pivotably supports the upper rear portion of the rear transducer mount support plate, by a fourth, lower rear pivot joint which includes a laterally inwardly protruding pivot pin.
With the construction described above, the rear transducer mount support plate, transducer mount assembly, and fore-and-aft oriented lower horizontal linkage bar comprise a four-bar, parallelogram linkage mechanism which enables the transducer mount assembly to move relative to the Z-axis tool support platform only in a vertical direction, i.e., parallel to the front surface of the Z-axis platform. The four-bar linkage mechanism consists of (1) an upper horizontal linkage bar comprising an outer lateral side portion of the rear transducer mount support plate which has a forward protruding arm and which is pivotably supported at the rear end thereof by a buttress wall protruding from the Z-axis platform, (2) a front vertical linkage bar comprising a vertically downwardly disposed rear side web of the transducer mount assembly which is pivotably fastened at the upper end thereof to the inner side of the support plate arm, (3) a lower rearwardly disposed lower horizontal linkage bar which is pivotably fastened at the front end thereof to the lower end of the transducer mount assembly side web, and (4) a rear vertical linkage bar comprising the vertically disposed buttress support wall which pivotably supports near its upper end the rear transducer mount support plate, and which is pivotably supports near its lower end the rear end of the lower horizontal linkage bar.
The automatic bonding machine according to the present invention includes an ultrasonic force-producing transducer which is fastened to the transducer mount assembly, and an ultrasonic bonding tool attached to the transducer which protrudes downwardly from the front lower end portion of the transducer, the latter being located near the front, lower end of the transducer mount assembly. A compression spring disposed between a vertical lever arm laterally offset from and attached to the rear transducer mount support plate, and the Z-axis tool support platform, resiliently biases the transducer mount assembly and ultrasonic bonding tool tip in a vertically downward direction relative to the Z-axis tool support platform. This construction enables the tool tip, transducer and transducer mount assembly, and rear transducer mount support plate to move resiliently upwardly when the tool tip is moved downwards into contact with a bond site to effect a bond, thereby limiting downward force exerted by the tool tip on a bond site to a value adjustable by adjusting the spring constant or spring preload. Preferably, resilient upward displacement of the transducer mount assembly is also used to open a pair of electrical switch contacts, thereby providing a logic signal which initiates application of an electrical current pulse of a pre-determined duration to the ultrasonic transducer.
A preferred embodiment of an automatic ultrasonic bonding machine according to the present invention also includes a wire spool for holding a supply of bonding wire, a drag tube assembly for exerting a rearwardly directed frictional force which resists forward motion of the wire from the spool, a clamp assembly for grasping the upper end of a wire protruding through the bore of the bonding tool to grasp, pull and thereby sever the wire after formation of a bond, a platform pivotably mounted on the upper side of the transducer mount assembly for pivotably supporting the clamp assembly and drag tube relative to the transducer mount assembly and the transducer, a clamp/drag tube pivot support platform actuator, an electronic flame-off torch pivotably mounted to the underside of transducer mount assembly, and an electronic flame-off torch pivot support actuator. The function of the foregoing elements is described below.
An automatic ultrasonic bonding machine according to the present invention also includes a Y-axis motor for driving the Y-axis tool support platform and rollably attached X-axis and Z-axis platforms to position the tip of the ultrasonic bonding tool at precisely determinable Y-coordinates relative to a workpiece. The machine also includes an X-axis motor for driving the X-axis tool support platform and rollably attached Z-axis tool support platform to position the tool tip at precisely pre-determinable X-axis positions relative to a workpiece, and a Z-axis motor for driving the Z-axis tool support platform to position the tool tip at precisely pre-determinable Z-axis locations.
In a typical application of an automatic ultrasonic bonding machine according to the present invention, a pattern recognition television camera, camera monitor and computer are functionally interconnected to provide position command signals to the tool support platform drive motors, and to other actuator mechanisms of the machine. Operation of the machine typically includes the steps of feeding bonding wire from the supply spool down through the drag tube, open clamp jaws, upper entrance opening to the bore through the ultrasonic bonding tool, and outwardly from the lower exit opening of the bonding tool bore. The protruding end of the wire is then brought into contact with a bonding site on a test surface by the tool support platform drive motors in response to command signals issued by the computer. A command is then issued by the computer to energize the ultrasonic transducer with an electrical impulse of a pre-determined duration, thus forming a wedge bond between the wire end and the bond site on the test surface. Command signals are then issued to close the clamp jaws on the length of wire between the bonding tool and drag tube, and to translate the Z-axis tool support platform upwardly sufficiently far to sever the wire end at the bond site. A command signal is then issued to pivot the support platform for the drag tube and clamp assembly vertically downwards a pre-determined distance, thus extending the severed wire end a pre-determined distance below the lower exit opening of the tool tip bore. Next, a command signal is issued to pivot the end of the electronic flame-off torch downwardly and forwardly to a location below the wire end, and a signal issued to initiate an electrical arc discharge of pre-determined energy and duration between the tip of the electronic flame-off torch and the end of the wire, thus causing the end of the wire to melt and resolidify to form thereat a fusion ball of pre-determined characteristics, including size, shape and crystalline structure. The clamp jaws are then released and the drag tube and clamp support platform pivoted upwards to its rest position. During this step, rearwardly directed tension is exerted on the bonding wire by frictional contact between inner wall surface of the drag tube bore and the wire therewithin. This tension pulls the wire taut, thus insuring that the fusion ball is seated on the lower surface of the bonding tool tip. The tool tip is then translated horizontally and downwardly towards a pre-determined bonding site on a workpiece. The bonding tool is then brought into contact with a bonding site, and a pulse of ultrasonic bonding energy of a pre-determined duration is applied to the ultrasonic transducer, that energy being coupled through the tool to its tip and thus forming an ultrasonic bond at the site. The tool tip may be moved to a different location to form a second bond, or additional bonds. After the first bond, or the last bond in a sequence has been made using the same wire, the jaw clamps are closed and the Z-axis tool support platform translated upwardly to sever the wire, thus completing a bonding cycle, which may be repeated at a rate of 5 to 10 bond cycles per second.
In the preferred embodiment, the pattern recognition camera and computer cooperate to provide command signals to the positioning and actuating mechanisms of the machine which enable the machine to repeat the bonding steps described above at high rates on pre-determined locations of workpieces which are identified by pattern recognition software.